Cloning and expression of immunoglobulin D heavy chain in mandarin fish,Siniperca chuatsi

Full cDNA sequence of membrane-bounded immunoglobulin D(mIgD)heavy chain in the mandarin fish,Siniperca chuatsi has been isolated and characterized using RACE-PCR and RT-PCR methods.The mandarin fish' mIgD gene consists of 3 358 nucleotides including 5lUTR of 30 nucleotides,3l UTR of 337 nucleotides and an open reading frame with 2 991 nucleotides encoding 996 amino acid residues.The structure of mandarin fish'mIgD contained the VDJ region,the constant region of μ1-δ1-δ2-δ3-δ4-δ5-δ6-δ7,and TM region.The amino acid sequence of the constant region of mandarin fish mIgD shared 37%-72% identity with those of previously reported teleost IgDs including conserved cysteines and tryptophans.Phylogenetic tree based on teleost IgD heavy chain constant regions generated by Neighbor Joining method suggests that all teleosts cluster together,and that the mandarin fish'mIgD is clustered closely with Japanese flounder's IgD and Atlantic halibut's IgD.Real-time PCR showed that the mandarin fish'mIgD transcription was mainly detected in peripheral blood leucocytes(PBLs),thymus,head kidney,kidney and spleen.